Friday rush hour. Euston station. Who's here? Who isn't. A kaleidoscope of skin colours. The world in one terminus. Barbara Roche can see it over the rim of her cup of Americano coffee. "I love the diversity of London," she tells me. "I just feel comfortable."

We haven't spoken since she was in government and it's nice, but we're here on business. There is a narrative that says that Labour didn't just fail to control immigration but that it deliberately opened the floodgates so that millions would flow in and then vote Labour. "Was mass immigration a Labour conspiracy?" asked the Daily Mail last week, primed by the henny penny specialists at Migration Watch.

The best evidence for this is a 2009 article in the Evening Standard by Andrew Neather, who said that while working within government on a landmark speech, he gained the "clear sense" that immigration policy "was intended – even if this wasn't its main purpose – to rub the right's nose in diversity".

Roche was immigration minister at the time. The speech, 11 years ago, was her speech. So if there was a conspiracy, she would have been up to her neck in it. Only, she says, there wasn't and so she wasn't. "I was puzzled when that was written and I'm no less puzzled now," she says. "It's strange. I was accused by some of being too robust and now it's said I went for unrestricted migration. I have never been in favour of unrestricted migration. But it was a landmark speech. When I arrived at the Home Office there was no coherent migration policy. I wanted to be the first minister to say that migration is a good thing. It is."

There were drafts of the speech, some more radical on the economic benefits than others. There was also parallel wonking under way in Downing Street. "But if there was a secret policy, someone would have let me in on it," says Roche, who now chairs a housing association and a group setting up a museum of migration. There were challenges, she says, successes, failures. The cock-ups we know. Even Ed Miliband admits to that. But no dastardly conspiracy. Still, the hare is loose and there's no catching it. So the story will run and run just the same.